Abstract: An apparatus for receiving optically encoded binary data transmitted over an optical fiber from an optical transmitter device coupled to another data processing system. The receiver apparatus is used to convert the light signal carrying the subject data into TTL level digital logic signals. The receiver apparatus is comprised of circuitry for converting the optically encoded data into electrical signals in serial format, and circuitry for converting these electrical signals into TTL level digital signals in parallel format for use by a user device. The primary advantage of the apparatus disclosed here is the ability to substitute a single optical fiber for a plurality of parallel copper wires for carrying data between one data processing device and another with little or no loss in speed due to the larger bandwidth of optical fibers.